"I'm under all kinds of pressures you don't even know about because I protect them from you, so give me a break if occasionally I'm short with you."
A former excellent (no, I'm not brownnosing) boss of mine told me, "Employees who do well are ones who try to understand the whole picture. Some people take decisions personally when, in fact, the decision has nothing to do with individuals and is about furthering the health of the business overall. In other words, this is not about you." Here's an exercise in empathy: Imagine you were your boss. After mentally rearranging the stuff in her/your office, think about all the people she/you answer to and all the forces at play that her/your employees don't have to deal with. And be thankful that all you get is a snippy reply to something, rather than a chewing-out from the CEO.